Disclosing light

ABSTRACT

For dental, medical and other uses, with a disclosant phosphordye such as sodium fluorescein, a disclosing light emitting radiation substantially confined to the wavelength range between 380 and 505 nanometers (nm.) and free from infrared, yellow and ultraviolet. The light includes a source of light, which can be an incandescent lamp, a dichroic reflector behind it to reflect blue light forwardly and transmit the rest backwardly, a dichroic filter in front of the lamp to transmit blue light and reflect the infrared backwardly, and a viewing mirror for the parts irradiated, the mirror reflecting yellow light toward the observer and transmitting the other radiations. The ultraviolet, although it would excite the fluorescein, is filtered out because it would also make the natural teeth, and some kinds of artificial teeth, fluoresce and obscure the fluorescence of the fluorescein.

United States Patent 91 Westlund, Jr. et a1.

[ 51 Jan. 16, 1973 1 DISCLOSING LIGHT [75] Inventors: Arnold E.Westlund, Jr., Manchester; Emery G. Audesse, Salem, both of Mass.

[73] Assignee: GTE Sylvania Incorporated [22] Filed: May 10, 1971 211Appl. No 141,742

[52] US. Cl. ..240/4l.l5, 128/22, 128/23, 240/4659, 350/1, 350/311 [51]Int. Cl. ..A6lb 1/06 [58] Field of Search ....350/1, 311;240/41.15,46.59; 128/22, 23

[56] References Cited UN lTED STATES PATENTS 2,798,943 7/1957 Prideaux..350/l X 3,459,178 8/1969 Fleming ..l28/22 3,325,666 6/1967 Bird et a1...35()/l UX 3,255,342 6/1966 Seitz et al. ..240/4l.l5 X

OTHER PUBLICATIONS Schroeder et al., A Commercial Cold Reflector, Jour.of the SMPTE, Vol. 69, No. 5, May 1960, pps. 351-354.

Primary ExaminerDavid Schonberg Assistant ExaminerToby H. KusmerAttorney-Norman J. OMalley, Laurence Burns and Joseph C. Ryan [57]ABSTRACT For dental, medical and other uses, with a disclosantphosphor-dye such as sodium fluorescein, a disclosing light emittingradiation substantially confined to the wavelength range between 380 and505 nanometers (nm.) and free from infrared, yellow and ultraviolet. Thelight includes a source of light, which can be an incandescent lamp, adichroic reflector behind it to reflect blue light forwardly andtransmit the rest backwardly, a dichroic filter in front of the lamp totransmit blue light and reflect the radiated, the mirror reflectingyellow light toward the observer and transmitting the other radiationsThe ultraviolet, although it would excite the fluorescein, is

filtered out because it would also make the natural teeth, and somekinds of artificial teeth, fluorescc and obscure the fluorescence of thefluorescein.

1 Claim, 4 Drawing Figures 0R mew/41. 5

infrared, backwardly, and a viewing n i ror for the parts ir-PATENTEDJAH 16 I975 RELATIVE ENERGY SHEET 1 or 2 FIG.I

400 500 600 700 800 EMITTED LIGHT WAVELENGTH IN NANOMETERS MW m,

ATTORNEY PATENTEBJAMSIHH 3.711.700

sum 2 or 2 EMERY G.AUDESSE ARNOLD E. WESTLUND JR.

INVENTORS BYWMI ATTORNEY DISCLOSING ueur This invention relates toelectric lighting devices, and 5 particularly to devices for dental andmedical purposes, such as viewing a persons teeth for plaque, tartar(technically called calculus) and the like, and for examining the skinand eyes. Such devices are often called disclosing lights.

2. BriefSummary of Prior Art Devices for this purpose have previouslyused ultraviolet light from incandescent lamps with Wratten type filtersor blacklight lamps. The former were inefflcient and yielded very littlelight on the person, and'the latter were cumbersome and presented apossible radiant energy hazard, because of the increased ultravioletlight.

In using the device, the teeth or other portions of the body to beobserved were first treated with a 20 fluorescent material, a small dropgenerally being sufficient for use on teeth, and the resultantfluorescence observed.

It has been suggested to use on the teeth or other parts to be observeda phosphor-dye excitable to fluorescence by visible light, with a filterto absorb the visible light on both sides of the absorption curve,although the excitation curve, which is the important. one, was notmentioned.

BRIEF DESCRIPTION OF THE INVENTION We have discovered that the use ofultraviolet in a disclosing lamp was ineffective with a phosphor-dyesuch as fluorescein, because the teeth themselves 35 fluoresce white andthis is not in much contrast to the yellow fluorescence of the sodiumfluorescein. We have further discovered that in cutting off part of theexcitation and absorption bands by keeping the exciting radiation above380 nm. (nanometers), that, is above the ultraviolet, and keeping theexciting radiation largely below 525 nm., which means substantiallyconfining it to the violet and blue, with its peak in the latter, we canobtain very good yellow fluorescence from the fluorescein in contrast tothe nearly dark background provided by the teeth themselves.

This was unexpected, because the wavelengths exciting sodium fluoresceinwere left in some doubt by the prior art, and The Merck Index-anEncyclopedia of Chemicals and Drugs (8th Ed. 1968; Merk & Co., Rahway,N. 1.), states that sodium fluorescein responds best to radiation of3600 Angstrom Units (360 nm.), which is in the ultraviolet region. ThePharmacological Basis of Therapeutics" (4th Ed.) by Goodman and Gilman,says that the absorption maximum in water is 4935 Angstrom Units (493.5nm.), but this only adds to the confusion, and in any event theabsorption maximum is not necessarily the excitation maximum. Even anon-fluorescent material has an absorption maximum, although it doesn'thave an excitation maximum, nor any excitation at all.

We have discovered that in order to get the maximum excitation and themaximum effect from the yellow fluorescence, the cutoff of the lightoutput from the disclosing lamp must have a very sharp cutoff at about525 nm. to emit as much as possible of the exciting visible lightwithout emitting any appreciable light of the color of the fluoresceinfluorescence. This can be achieved with ,a dichroic or interferencefilter infront of an electric lamp such as an incandescent lamp. Thefilter will transmit between 380 nm. and 525 nm., and cut offelswhere.

To emphasize the desired spectral pattern further, a dichroic reflectorcan be used behind the lamp, to reflect forwardly light of380 525 nm.and transmit the infrared b ackwardly and out of the beam. The reflector0 can reflect all of the visible light if desired, and the burden ofcutting out the undesired wavelengths be put on the filter.

When using the device, stray ambient light can obscure the fluorescenceby illuminating the teeth directly, but we have found that the use of adichroic mirror for viewing the irradiated teeth is very effective, ifit is designed to reflect light in the yellow, or emitting, range, buttransmit blue light and infrared, which will therefore not affect theobserver. To prevent the ambient light from passing through the mirrortoward the observer, a shield is preferably provided in back of themirror and spaced therefrom. The spacing gives a region in which theradiations transmitted from the front of the mirror are trapped. Theshield and any walls which define the space around the mirror shouldhave low reflectivity. The yellow light to be reflected would be betweenabout 560 and 590 nm. A person can then shine the light on his teeth andobserve the results in the mirror.

Because of the nature of dichroics, the filter in front of the lamp willalso transmit some of the very far red between 700 to 800 nanometers,but this will not affect the operation of the device, because of theextremely low sensitivity of the eye to such far red light.

Mimr tllefilt qyill n ottgansmit infrared adiation,

but will reflect it 95, which Fre'VfifiifiTheatin the portion of tliebody on which the radiation falls. This heating effect of the infraredcould otherwise be quite serious.

The result can be a very compact disclosing lamp for medical and dentalpurposes, although if desired, the filter and a suitable lamp or lampscan be used in a large, overhead fixture, or in other ways.

The device is, however, especially useful in the form of a lighting unitfor observing a small area.

The lamp, filter and reflector can be held in position in a plastichousing, and in a portable unit the reflector could preferably, for mostpurposes, bring the light to a focus about 2 to 4 inches in front of thefilter.

The dichroic coatings can be made in the usual manner for such coatings,that is, they can be built up on a backing plate of glass, for examplewith a series of alternate layers ofmagncsium fluoride and zinc sulfide,each layer being about a quarter wavelength thick.

The spectral transmittance characteristics of this coating for normalincident light should be as follows for greatest effectiveness: p

l. The average transmittance should be greater than 80 percent between380 and 490 nm.,as measured in 10 nm. increments, and no individualvalley should be less than 70 percent 2. The 50 percent transmittancepoint in the bluegreen wavelengths should lie between 495 and 505 nm.

3. The 10 percent transmittance point in the bluegreen wavelengthsshould lie between 510 and 525 nm.

Transmittance between 550 and 660 nm should be less than 2 percent.

Some deviation from these requirements is permissible, but the greaterthe deviation the less will be the effectiveness.

A switch for turning the lamp off and on can be incorporated in thedevice, so that the user will have everything under his immediatecontrol.

BRIEF DESCRIPTION OF DRAWINGS Other objects, features and advantages ofthe invention will be apparent from the following specification taken inconnection with the accompanying drawings, in which:

FIG. 1 is a longitudinal cross section of a device according to theinvention;

FIG. 2 is a spectral energy distribution curve of the light output ofthe device;

FIG. 3 is a plan view of the device; and

FIG. 4 is a front elevation of the device.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, the tubularincandescent lamp 1 is shown held by its base 2 in the usual contactreceptacle 3, into which the usual threaded portion 4 of the base fits,and which is attached to the housing 5. In the customary manner, thereceptacle 3 makes electrical contact with the outer metal shell 6 ofthe base, and with the eyelet contact 8 of the base 2, said eyeletcontact being attached to the outer metal shell through the insulatingglass plug 9 in the manner customary in the art.

The lead-in wires 10,11 extend out of the housing through a bushing 12,held in the usual manner by a nut 13 on a threaded portion 14 of saidbushing 12. Wire is electrically connected to the helical coil 3 andwire 11 extends through on-off switch 15 and wire 16 to the socket. Thewires are covered with insulation.

The push button 17 actuates the switch 15 in the usual manner, being setinto the housing 5.

The filament in lamp 1 is at or near the focus of the reflector 18,which in the embodiment shown is an ellipsoid having one focussubstantially at the lamp filament and the other focus a few inches, sayfrom 2 to 4 inches, in front of the device. The reflector 18, which canbe a surface of revolution, is of glass having a dichroic coating on itsreflecting surface. The dichroic coating is designed to reflect visiblelight and transmit infrared.

In front of the reflector is the dichroic filter 20, which is flat, thisreflects yellow and infrared back into the housing, and transmits blue,which is roughly the opposite of what the reflector 18 does. The edge 21of the reflector 18 is spaced from the filter 20 by a coiled spring 21which bears against the edge frame 22 of filter 20, reflector 18 beingpushed back by the spring 21 to seat against the stop 22 in housing 5.

The dichroic mirror 23 is set on a projecting enclosing bracket 24 atthe top front of the casing 5. The mirror is dichroic, reflecting yellowand transmitting blue and infrared, and is set at an angle to a planetransverse to thelongitudinal axis of the optical system, whichcomprises reflector l8, lamp 1 and filter 20, and is in position toreflect rays from the teeth or the like to the eye of the viewer. Anangle of approximately 10 has been found very effective for theembodiment described, although the angle can be varied between 5 and 16with good results.

The outer details of the housing are shown in FIGS. 3 and 4. When thewords top," front" and the like are used herein, they refer to thecorresponding portions of the device when in the position shown in FIG.I, that with the mirror 23 at the top, and with the end of the housingat filter 20 being considered the front, since it is the place wherelight emerges from the device.

In FIG. 2, the spectral energy distribution of the device is shown. Thelight output is seen to peak in the blue at about 490 nanometers and toextend from about 380 nanometers to about 525 nanometers, that is, fromthe violet to the green. There is no appreciable light in the yellow andorange but there is a narrow peak in the far red, which is unimportantbecause the sensitivity of the eye is very low in that region. FIG. 2shows the energy distribution of the radiation from the device, and notthe effect on the eye.

The front view of FIG. 3 shows the viewing mirror 23 the bracket 24holding it, the face plate 25, the front of housing 5 and button 17. Theprofile in FIG. 4 shows the housing 5, the bushing 12 and the pushbutton 17. Other styling than that shown can be used.

The dichroic coatings used in the embodiment described were deposited onglass plates which had a thickness between 0.047 to 0.062 inch. The lamp1 was an l8-watt appliance lamp in a T7 bulb, that is in a bulb tubularin shape and seven-eighths inch in diameter.

This is a vacuum lamp in which the tungsten filament operates at acomparatively low temperature, less than in the usual gas filled bulb,so the ultraviolet emitted from the filament is small, and the glass ofthe bulb cuts it down somewhat more. The filter 20 has a fairly sharpcutoff between 350 and 380 nm. so that it also cuts out some of theresidual ultraviolet, but this ultraviolet cut off from the filter isless necessary than it would be with a higher ultraviolet-contentsource.

The filter 20 used in the specific embodiment described had aboutpercent transmittance at 380 nm., about 50 percent at 370 nm. and 8percent at 350 nm. On the other end of the transmitted region, thetransmission was slightly above 80 percent at 490 nm., about 60 percentat 500 nm 40 percent at 505 nm. and 6 percent at 525 nm.

The filter 20 used was a dichroic, or interference filter, withalternate quarter-wavelength thick layers of magnesium fluoride and zincsulfide. The layers were deposited on light-transmissive glass backingplate, the layer on the glass being the fluoride, for good adherence,and the top, or thirteenth layer being of the fluoride, which gives aharder surface than the sulfide. The mirror 23 in which the teeth wereviewed was the same.

The reflector 18 has 20 layers, each about onequarter wavelength thick,the one on the glass being magnesium fluoride. The layers then alternateending in a zinc sulfide layer on the outer surface.

The coatings can be applied in the usual manner for dichroics.

Although a specific embodiment has been described above, variousmodifications and alterations will be apparent to a worker skilled inthe art after reading the above specification, without departing fromthe spirit and scope of the invention, which is limited only by theclaims.

What we claim is:

l. A disclosing light for self-examination of teeth treated with aphosphor dye excitable to fluorescence by visible light comprising: ahousing containing an incandescent lamp; a dichroic reflector withinsaid housing behind said lamp in position to reflect blue light andtransmit infrared radiation; a filter within said housing in front ofsaid lamp for transmitting blue light and reflecting back yellow lightand infrared radiation, said filter having an average transmittancegreater than 80 percent between 380 and 490 nm., as measured in nm.increments, and is not less than percent for any wavelength in thatrange, and in which the 50 percent transmittance point is between 490and 505 nm., with the 10 percent transmittance point in the blue-greenwavelengths between 510 and 525, with the transmittance between 550 and660 nm. less than 2 percent; a dichroic viewing mirror attached to saidhousing and outside it in position such that a viewer using the light onhis teeth can see the result in said mirror, the transmittance andreflectance characteristics of said mirror being about the same as ofsaid filter; and a shield disposed behind said mirror to prevent ambientlight from passing through said mirror toward said viewer.

